FIG. 1 shows a component parts chart of various sewing machine related components (FIG. 1 was printed Oct. 3, 2007 from http://hirose.s-club.net/en/chart.htm).
FIG. 2 shows types of hook gibs for sewing machines (FIG. 2 was printed Oct. 3, 2007 from http://hirose.s-club.net/en/hook.htm).
With reference to FIG. 2 in particular, it is noted that the so-called A-TYPE (Short gib) is said to be for sewing heavy material and zigzag sewing. This type of short gib is said to not keep the needle thread for as long a time as some other types of gibs and therefore does not cause trouble in connection with the thread passing (even if the hook is set at a rather late time against the needle).
Still referring to FIG. 2, it is noted that the so-called B-TYPE (Full gib) is said to be for general use and permits sewing from light to heavy materials. This type's special feature is said to be a long-extending gib, which serves to prevent excessive thread-loosening since it holds the needle thread for a relatively long time when it passes out from the hook. It is therefore said to be effective at preventing looping (the towel texture formed on the back of a cloth), which is apt to appear when strongly twisted or rough thread is used.
Still referring to FIG. 2, it is noted that the so-called C-TYPE (Tacking gib) is said to be used for medium and light materials. It has a projection to prevent the needle thread from entering into a gap between the race way of the hook and the race of the bobbin case holder when it is passing through. This projection is said to keep the thread on itself and not only prevents the thread jamming, but also lessens an unnecessary thread loosening to a certain degree by holding the thread.
Furthermore, due to this projection, the race way of the hook is extended in length, which is effective to increase durability and reduce its noise.
Still referring to FIG. 2, it is noted that the so-called D-TYPE gib is said to be designed for sewing light materials (this type of gib is said to have the advantages of both B-type and C-type.) Namely, it has a gib like B-type's for holding the thread and a projection like C-type's to prevent thread jamming. Another feature on D-type is the lightness of the bobbin case holder, which is said to reduce its moment of inertia and lessen the resistant force that occurs when the thread passes through the position bracket (finger) of the bobbin case holder. This is said to ensure smooth sewing when using a fine or weak thread, or a synthetic fiber thread which is difficult to handle.
Still referring to FIG. 2, it is noted that the so-called BOH-TYPE gib is said to be for sewing medium and heavy materials. The gib is said to be comparatively short in length to ensure smooth thread-passing and to prevent looping (even when loosely-twisted, thick and soft thread is used).
Still referring to FIG. 2, it is noted that the so-called F-TYPE (Jamproof gib) is said to belong to the A-type. This type features a gib set on the hook body with stud screws and coil spring (jam proof). When jamming occurs, this structure is said to allow the thread to be taken away from the race without disassembling the rotating hook. This type is also said to be available for zigzag sewing for house-hold sewing machines.
Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. The figures constitute a part of this specification and include illustrative embodiments of the present invention and illustrate various objects and features thereof.